A few weeks ago I bought on eBay the latest Lars Audio Gigawork Balanced USB DAC W/ Headphone amplifier “DAC-2 BL” (version LM-DAC7 V3.2), based on the features and specs announced in the ebay’s ad. In description and in pictures provided it showed up-sampling module with CS8421. When I received the actual DAC, I have examined it and found that this module is missing, and instead there are four jumpers installed. I contacted the seller and he told me that this version goes without up-sampling and should work fine (it is). Make it short, I got the missing module from the seller, installed it, and it sounds fine as well with that module. At least, I cannot tell a difference, specially taken in account that the DAC is completely new and may require some burning.

So, I have two questions (sorry, I know, it was discussed thousand times):
1. Do I need up-sampling or not? I tried to read through hundreds of pages in some threads here and couldn’t get a straight answer.
2. Is there somewhere (on ebay?) a DIY module that could be plugged into this DAC to show a sampling rate of the input signal?
Any input is highly appreciated. I don’t mean to start a new long discussion, a link to the post where those questions are clarified would be sufficient.

The way those ASRC cips do the upsampling is not very... usefull. Especially if your source (transport) has a decent quality with low jitter.
Practically they don't bring up significant improvements of the sound quality, some say that even they mudd up the sound. So probably, what you hear is real...
Technically the upsampling process in those cips is simplistic, crude, due to the lack of processing power and buffer memory. The "correct" way to do it is using dedicated audio DSP cips (processors with sufficient speed and memory). DSP-way it is done in some high-end players, receivers.

Well, then feed it with native 24/96 signals
I did listen the ASRC made by TI and AD and was not happy with the results. AD was marginally better, but maybe was just my imagination. I still have to hear a CS one, but the principle of operation is not different from the others. No buffer for jitter reduction, single stage digital PLL loop, ROM coeficients used to guess the next sample...

Thank you, Sonic, for a link. Good selection for the tests.
But again, if original source is SACD, my Denon 3910 does pretty good job playing it. It would be nice to have the real 24/192 source.

Anyway, back to the topic. Right now I more interested to get the best from the red book cd. For that task considering the current chipset (receiver CS8416, DAC PCM1798 and Up sample rate converter CS8421), what would be in theory the better option: with up-sampling or without it?

PCM1798 is a good DAC. So it might not make a difference in the end.
I didn't listen the CS8421 ASRC, maybe you can do some A-B comparations. It also depends of the final amp/speaker/headphones if you can detect small differences.

PCM1798 is a good DAC. So it might not make a difference in the end.
I didn't listen the CS8421 ASRC, maybe you can do some A-B comparations. It also depends of the final amp/speaker/headphones if you can detect small differences.

I cannot see any difference between using CS8421 or not. At the same time the sound is tiny bit inferior to what I can get using Rotel RCD-950 analog RCA -> Classe, but better than one from my other CD players, including Denon 3910.

Now, here is a problem: after downloading 24/192 material I have discovered that my DAC does not play it. All previous sample files I used were 24/96